When Celine, played by Julie Delpy, first met Ethan Hawke's Jesse in "Before Sunrise" back in 1995, on a Budapest-to-Vienna train just made for postcollegiate flirtation, one round of small talk led to another, until the talk got a little bigger and phased into bleary-eyed, besotted exchanges about literature and life's fleeting romantic glories.

A lot of the talk was showboating, particularly with Hawke's aspiring novelist character, whose "act" seemed frequently at odds with the human being underneath the angles and gambits. By the end of director and co-writer Richard Linklater's beautiful film, you knew the performers had gone places most movies disallow their actors because most dialogue sequences — and "Before Sunrise," like its sequels, is a single, searching dialogue sequence — cut to the chase or the resolution.

In the second film, "Before Sunset" (2004), Jesse and Celine reunited after their Vienna evening and early morning, when the American visited Paris on a book tour. His novel had a lot to do with the woman, Celine, who got away. Jesse was married with a son by then. By the end of the picture, which (improbably) was just as lovely as the first, the stars appeared to align these two, though director Linklater's fade-out was at least a tiny bit ambiguous, enough to provoke one commenter on Internet Movie Database to ask: "Can someone explain the ending of this movie to me?" We'll all be asking that one someday, as our final credits roll.

"Before Midnight" answers a lot of questions, while adding a distinct element of melancholy. First things first: Linklater's reunion with these characters, and these actors, is well worth your time, especially if you've already made their acquaintance and you're interested in catching up. As in the ongoing Michael Apted "Up" documentary series, there's new light, different light and shade being cast on the subjects every time.

If "Before Midnight" is somewhat less special than its predecessors, well, it's tougher to tease out the allure and charm in the depiction of a long-term relationship (though it's certainly worth trying) than it is to simply ask the question: Are they going to get together? This one's set in Greece. A writers' retreat has brought Jesse to Messinia from Paris with Celine and their twin daughters (a screenful of curls played by Jennifer and Charlotte Prior).

At the start, Jesse's middle-school-age son (Seamus Davey-Fitzpatrick), who has just spent a fine summer with his father's newish family, is at the airport, heading back to the U.S. and his unseen mother, whom we hear is a "drunk" and "abusive psychologically." The boy we meet, albeit briefly, hides the shell shock well; he's a calm, easygoing, if somewhat beaten-down presence compared to his overeager and insecure father.

At dinner with their hosts, Jesse and Celine talk about everything from the ravages of social media to the challenges of their complicated relationship ("I'm actually surprised we lasted this long," Celine says). The chatter becomes somewhat agitated; Celine, between jobs, has grown itchy with her partner's well-practiced Moderately Famous Novelist routines. That night their Greek friends baby-sit the twins so they can get away for a night on their own. And then "Before Midnight" turns meaner, sadder than the two previous films. There's a chill in the air. "Do you ever listen to yourself?" spits an exasperated Jesse in the middle of a plausibly hideous argument.

Though this is his most effective screen work to date, I've always found Hawke in the "Before" films to be effective in a slightly showier and more calculating way than Delpy, who really does appear to be pulling each moment, each hairpin emotional curve, out of her own experience. Partly it's a technical matter: Hawke, a very busy performer, indulges himself with a few too many improvisatory conversational place holders, the "uhs" and the "yeah, but sees" and the verbal windups before the pitch. He has a way of dominating the talk, the way the character is meant to dominate. But Delpy has always challenged Hawke to find a simpler, more direct form of acting in Linklater's films, which gives them their unique suspense and rolling tension.

Where does this one end? I won't say, and I can't yet say the ending works for me, let alone how it might work for the IMDb.com commenter vexed by the warmer resolution of "Before Sunset." What Linklater, Delpy and Hawke have achieved with their trilogy is at once fluidly cinematic and novelistic, with stories behind the stories and possible endings beyond the endings we're given. These two, like so many of us, believe in the talking cure, even when it becomes a momentary, fractious curse. And they really do love each other. "Before Midnight" doesn't ask the question directly, thank God, but it encourages you to wonder: Is that enough? When does the knotty business of living outwit the love? Where will these two be in another nine or 10 years?